Electrical interconnect assembly

ABSTRACT

An electrical test contact electrically connects a test terminal of an Integrated Circuit (IC) test assembly with an IC terminal of an IC device in an electrical interconnect assembly. The test contact is formed of electrically conductive material and includes a head portion and a foot portion. The head portion includes a first electrical contacting portion for electrically engaging an IC terminal of an IC device during use, and the foot portion includes a second electrical contacting portion for electrically engaging a test terminal of a test assembly during use. The head portion includes a head receiving portion that receives a first resiliently biasing member to retain the first resiliently biasing member in contact with the test contact. The first resiliently biasing member biases the first electrical contacting portion against the IC terminal of the IC device during use. An electrical interconnect assembly having multiple test contacts is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/122,219, filed Nov. 25, 2013, now U.S. Pat. No. 8,952,714 which isthe national stage of International Application No. PCT/MY2011/000058,filed on May 27, 2011. The foregoing applications are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to an electrical interconnect assembly foruse in testing integrated circuit (IC) devices and to a test contact foruse in an electrical interconnect assembly.

BACKGROUND OF THE INVENTION

As part of an IC manufacturing process, it is important to testmanufactured IC devices in order to ensure that the devices areoperating correctly and to required specifications. Such testing isgenerally carried out using an IC test system, the test system having atest assembly and an interconnect assembly arranged to electricallyconnect the test assembly with pads/leads of an IC during testing sothat characteristics of the IC device in response to input electricalstimuli can be determined and compared with reference responses by thetest assembly. The interconnect assembly comprises a series of testcontacts which extend between respective test terminals of the testassembly and IC terminals of the IC device. The test assembly isarranged to provide an interface between a test assembly and an ICdevice whilst minimizing the likelihood of damage to leads/pads of theIC device.

In one arrangement, the interconnect assembly includes first and secondarm portions arranged to respectively connect with test terminals and ICterminals. The test contacts are moveably disposed in the interconnectassembly and resiliently biased such that during use, when an IC deviceis engaged with the test assembly, a biasing force is exerted so as tourge the first arm portion into good electrical contact with an ICterminal of an IC device and so as to urge the second arm portion intogood electrical contact with a test terminal of the test assembly. Thetest contacts in this arrangement, however, can transfer excessive forceto the test terminal resulting in premature wear of the test terminaland can damage the IC terminal during use.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided an electrical test contact for electrically connecting a testterminal of an IC test assembly with an IC terminal of an IC device inan electrical interconnect assembly, the test contact being formed ofelectrically conductive material and comprising:

-   -   a head portion; and    -   a foot portion;    -   the head portion comprising a first electrical contacting        portion for electrically engaging an IC terminal of an IC device        during use, and the foot portion comprising a second electrical        contacting portion for electrically engaging a test terminal of        a test assembly during use, the first and second electrical        contacting portions being substantially oppositely located on        the test contact; wherein    -   the head portion comprises a head receiving portion arranged to        receive a first resiliently biasing member to thereby retain the        first resiliently biasing member in contact with the test        contact; and wherein    -   the first resiliently biasing member is arranged to bias the        first electrical contacting portion against the IC terminal of        the IC device during use.

In one embodiment, the head receiving portion restricts the test contactfrom moving laterally relative to a vertical plane intersecting the testterminal. In another embodiment, the head receiving portion restrictsthe test contact from moving vertically relative to the vertical planeintersecting the test terminal. That is, the retention of the firstresiliently biasing member reduces vibration and enhances stability,rigidity and co-planarity of the test contact, in particular, duringuse.

In one embodiment, the first resiliently biasing member (e.g. topelastomer) is located vertically under the first electrical contactingportion (e.g. direct contact area) to absorb the force exerted on thetest contact (e.g. test pin) during use The top elastomer may also bepre-tensioned and is held in place by the head receiving portion of thetest pin so that during use the pin only moves vertically downwardrelative to a vertical plane intersecting the test pin. Thus, by holdingthe pin in this manner, the test assembly avoids vibration generatedduring use and only provides a small indent mark on the test terminalrather than a long scratching mark or wiping. This motion also reducespre-mature wearing of the IC terminals (e.g. contact pins) and improvestheir lifespan and test yield.

In one embodiment, the head receiving portion exerts a clamping force onthe first resiliently biasing member to retain the test contact to thefirst resiliently biasing member, The head receiving portion may be atleast partially circular. In an example of the test contact in use, thetest contact retains the first resiliently biasing member to providebetter alignment of the test contact with the corresponding IC terminalof an IC device being tested. The test contact thus minimizes itslateral movement during use and minimizes wear of the corresponding ICterminal (e.g. by scratching).

In one embodiment, the foot portion comprises a foot receiving portionarranged to receive a second resiliently biasing member. The footreceiving portion may also be at least partially circular. in theembodiment, the second resiliently biasing member biases the secondelectrical contacting portion against the test terminal of the testassembly during use. Also, the second resiliently biasing memberdecelerates force exerted on the test terminal of the test assembly bythe second electrical contacting portion during use.

In one embodiment, the second electrical contacting portion comprises aprofile for ratably engaging the test terminal of the test assemblyduring use. With this embodiment, the profile comprises a curved surfacearranged such that during use rotation of the test contact effectsregulation of the contact pressure between the test contact and the testterminal. Also, in an arrangement, the curved surface effects rotationalmovement of the test contact during use (e.g. a see-saw movement). In anexample, the test contact minimizes wear from, for example, indentingthe test terminals and the supporting load-board when used. Thus, inuse, force is applied on the test contact which is distributed to thefirst resiliently biasing member acting as a vibration dampener andforce dissipater. The test contact is moved down vertically so that itssecond electrical contacting portion (e.g. load-board contact radius)acts as a fulcrum (e.g. contact surface pivot point) which distributesforce to the second resiliently biasing member (e.g. rear elastomer). Inan arrangement, the rear elastomer is also pre-tensioned and the footreceiving portion retains the rear elastomer to the test contact tominimize vibration. In this case, the second biasing member also acts ascounter force generator and a force dissipater to protect the load-boardagainst wear or damage whilst maintaining contact with the load-board.Also, the profile of the test contact enables, after force is applied tothe top of the test contact, the contact surface to contact theload-board without excessive pressure by diverting away some of theforce with a sliding action/motion towards the second resilientlybiasing member.

The test contact may be formed of metal material, such as precious metalmaterial, and in one arrangement, the metal material comprises NiPdAuplating. It will be appreciated by those persons skilled in the art thatthe material may comprise NiPd plating, Au plating, or another platingmaterial possessing desirable properties, such as desirable hardness anddurability. It will also be appreciated that the hard plating (e.g.NiPd/NiPdAu) can cause test contacts to wear prematurely under highforce and vibration.

In one embodiment, the first and/or the second electrical contactingportions is/are arranged to facilitate sliding of the first and/or thesecond electrical contacting portion relative to the respective ICterminal or test terminal. The first and/or the second electricalcontacting portion may comprise beryllium copper material.

In one arrangement, the first electrical contacting portion comprises aprofile arranged to facilitate sliding of the first electricalcontacting relative to the IC terminal.

In one embodiment, the foot portion comprises a thickness greater than athickness of the head portion. With this embodiment, the thickness ofthe head portion may be less than the width of an IC terminal of an ICdevice desired to be tested. In an alternative embodiment, the headportion comprises a thickness greater than a thickness of the footportion.

In one embodiment, the first resiliently biasing member comprises anelastomeric member, Also, the second resiliently biasing member maycomprise an elastomeric member.

In accordance with a first aspect of the present invention, there isprovided an electrical interconnect assembly for electrically connectingtest terminals of an IC test assembly with respective IC terminals of anIC device, the electrical interconnect assembly comprising:

-   -   a first resiliently biasing member;    -   a plurality of test contacts as claimed in any one of the        preceding claims, each of the test contacts being retained in        contact with the first resiliently biasing member; and    -   a housing provided with a plurality of contact sockets, each        contact socket being arranged to receive a test contact such        that the test contact is movable during use relative to the        contact socket; wherein    -   the first resiliently biasing member arranged to bias the        respective first electrical contacting portions against the IC        terminals of the IC device during use.

In one embodiment, the first and second resiliently biasing memberscomprise respective elongate elastomeric members, which may besubstantially cylindrical. While the elastomeric members are generallycylindrical in this embodiment, it will be understood that any suitableshape is envisaged.

In an embodiment, the second resiliently biasing member prevents thetest contacts from contacting the housing, in particular thecorresponding contact sockets, with excessive force. Thus, in theembodiment, the second resiliently biasing member provides safety forthe sockets and prevents the test contacts from over travelling theirhome position in their respective sockets by acting like a verticalspring loaded pin. The second biasing member also decelerates forceapplied to the test contacts, during testing, and pushes the testcontacts back to their home position without excessive stress on theload-board to prolong load-board life and to improve test yield.

In one embodiment, each contact socket is configured such that thecontact socket is keyed to the foot portion so that the amount ofpermitted rotation of the test contact relative to the respectivecontact socket is restricted. In this embodiment, the contact socket mayalso comprise a stop to restrict rotation of the test contact. Eachcontact socket and stop further improves co-planarity of the testcontacts to minimize wear of the IC terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic cross-sectional view of a test system of thetype including a test assembly and an electrical interconnect assemblyin accordance with an embodiment of the present invention, and showing atest contact forming part of the interconnect assembly;

FIG. 2 is a diagrammatic cross-sectional view of a test contact formingpart of the interconnect assembly of FIG. 1;

FIG. 3 is a further diagrammatic cross-sectional view of the testcontact. of FIG. 2;

FIG. 4 is a further diagrammatic cross-sectional view of the testcontact of FIG. 2;

FIG. 5 is a diagrammatic perspective view of the test contact of FIG. 2;

FIG. 6 is diagrammatic cross-sectional view of a test system, andshowing an IC device disposed on the interconnect assembly of FIG. 1;

FIG. 7 is diagrammatic cross-sectional view of a test system, andshowing an IC device disposed on the interconnect assembly of FIG. 1 inuse;

FIG. 8 is a further diagrammatic cross-sectional view of the theinterconnect assembly of FIG. 1; and

FIG. 9 is a diagrammatic perspective view of an interconnect assembly inaccordance with an embodiment of the invention, and showing a pluralityof test contacts of the type shown in FIG. 2.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Referring to FIG. 1, a test system 8 is shown for testing IC devices.The test system 8 is of a type including an electrical interconnectassembly 10 according to an embodiment of the present invention forforming an electrical connection between test terminals 12 of a testassembly 14 and IC terminals 15 of an IC device 16 desired to be tested.The test terminals 12 are located on a load-board of the test assembly14.

The test assembly 14 is arranged to carry out a series of tests on an ICdevice 16 connected to the test assembly 14 through the interconnectassembly 10, for example by applying defined signals to the testterminals 12, monitoring response signals and comparing the responsesignals to reference responses.

The interconnect assembly 10 comprises a housing 18 having a pluralityof test contacts 20, as shown in FIG. 4, movably disposed in respectivecontact sockets 22 formed in the housing 18. Each of the test contacts20 in this example is formed of electrically conductive material, forexample a NiPdAu plated material, and is formed of generally planarsheet-like material.

In the embodiment, each test contact 20 is generally L-shaped andincludes a first electrical contacting portion 24 arranged to engageduring use with an IC terminal 15 and a second electrical contactingportion 26 arranged to engage during use with a test terminal 12. Thetest contacts are arranged to engage with a first resiliently biasingmember 28, in this example in the form of an elongate generallycylindrical elastomeric member, which cooperates with the test contacts20 to urge the first electrical. Contacting portion 24 towards an. ICterminal 15, and to urge the second electrical contacting portion 26towards a test terminal 12. The test contacts 20 are prevented fromlateral and vertical movement relative to a vertical plane intersectingthe test contacts 20 by retaining in contact with the first biasingmember 28 with respective suitably shaped receiving portions. It can beseen in the Figures that the first biasing member 28 is mounted to thehousing 18.

In addition, it will be understood that the retention by the receivingportions reduces skewing of the test contacts 20 and thereby providesbetter co-planarity of test contacts 20. That is, the retention preventsthe contacts 20 from moving vertically and laterally relative to avertical plane intersecting the test terminals 15 to maintain alignmentwith the IC terminals 15 of an IC device 16 to be tested.

It can be seen from the Figures that test contacts 20 each comprise ahead portion 32 and a foot portion 34, and the head portion comprises ahead receiving portion 36 which is suitably shaped to exert a clampingforce on the cylindrical first resiliently biasing member 28 so that thehead receiving portions 36 is retained in contact with the firstresiliently biasing member 28. In particular, the receiving portion 36is shown as being partially circular to receive the first resilientmeans 28. That is, the receiving portion 36 exerts a pre-tension forceon the first resilient means 28 so that it can be retained.

During use, an IC device 16 to be tested is disposed on the interconnectassembly 10 and the IC device 16 is urged towards the interconnectassembly 10, as indicated by Arrow A shown in FIG. 3, in the directionof the vertical plane interesecting the test terminal. Once in thetesting position, the IC device 16 is secured in any appropriate way,for example using one or more screws. This causes establishment of goodelectrical contact between each first contacting portion 24 and an ICportion 15 and between each second contacting portion 26 and a testterminal 12, with each test contact 20 moving from a first positionshown by line 27 in FIG. 3 in the direction of Arrow A to a secondposition shown by line 25 in FIG. 3. As the test contact 20 movesbetween the first position and the second position, a small degree ofrotation occurs which causes a wiping action to occur at the ICterminals 15 and at the test terminals 12, thereby ensuring goodelectrical contact.

A test contact 20 in accordance with an embodiment of the presentinvention is shown in Figure SA, The test contact 20 comprises a headportion 32, a foot portion 34 and a receiving portion 36, as described,with the receiving portion 36 in this embodiment of generallypart-circular shape. The receiving portion 36 is configured to receivethe first biasing member 28 such that during use when an IC device 16being tested is engaged with the interconnect assembly 10 and the testcontact 20 moves from the first position to the second position, thebiasing member 28 is compressed and the biasing member 28 thereby exertsa biasing force on the IC terminals 15 and the test terminal 12.

That is, during use, the IC device 16 is urged towards the interconnectassembly 10, as indicated by Arrow A of FIG. 3, and the test contact 20is rotated to the second position shown by the line 25 in FIG. 3. Thehead portion 32 thus compresses the first biasing member 28 from afirst. position 35 shown in FIG. 2 to a second position 37 shown in FIG.3 and biases the test contact 20 back towards the first position. Also,the act of rotation of the test contact 20 urges the foot portion 38towards a second resiliently biasing member 29 which dampens therotation and biases the second electrical contacting portion 26 againstthe test terminal. 12 of the test assembly 10. Under rotation, thesecond resiliently biasing member 29 compresses from a first position 31shown in FIG. 1 to a second position 33 shown in FIG. 3 to dampen therotation and ensure that good electrical connection is made between thesecond electrical contacting portion 26 and the test terminal 12 but notso excessive so as to be detrimental to the test terminal 12. That is,the second resiliently biasing member 29 decelerates force exerted onthe test terminal 12 by the second electrical contacting portion 26during use minimize wear of the test terminal 12.

It can be seen that the second resiliently biasing member 29 is alsosubstantially cylindrical is shape and the foot portion 34 of the testcontact 20 comprises a foot receiving portion 38 arranged to receive thesecond resiliently biasing member 29. The foot receiving portion 38 isalso part circular and, in one example, may also be arranged to exert aclamping force on the second resiliently biasing member 29, providedthat the test contact 20 can still rotate and the second electricalcontacting portion 26 can rotably engage the test terminal 12. The first28 and second biasing members 29 are also fixed to the housing 18 andretained in contact with the test contact 20 by the respective clampingforces imparted by the head receiving portion 36 and the foot receivingportion 38 of the test contact 20.

In addition, the test contact 20 also includes a profile for rotablyengaging the test terminal 12. The profile comprises a curved contactsurface 30, part of which constitutes the second electrical contactingportion 26, such that during use the curved. contact surface 30regulates the contact pressure on the test terminal 12 to maintain agood electrical connect but minimize wear. In addition, the curvedsurface 30 enables the test contact 20 to regulate the contact pressureat the second electrical contacting portion 26 by self-adjusting itsorientation relative to the test terminal 12.

FIG. 4 shows the forces applied to the test contact 20 during use of thetest system 8. During use, the IC device 16 is urged towards theinterconnect assembly 10, as indicated by Arrows A, which imparts aforce to the test contact 20 and, in turn, to the first biasing member28 as shown by Arrow B. The first biasing member 28 acts as a dampenerand provides a counter force, shown by dotted arrow C, to the testcontact 20. The test contact 20 is moved down vertically with the curvedcontact surface 30 acting as a fulcrum to translate force to the secondresiliently biasing member 29 as shown by Arrow D. The second biasingmember 29 also provides a counter force, shown by dotted Arrow E, toprotect the load-board from wear.

The biasing force exerted by the first electrical contacting portion 24on an IC terminal 15 should also be sufficient to achieve goodelectrical contact, but not so excessive so as to be potentiallydetrimental to the IC terminal 15. Furthermore, in order to facilitategood sliding action with some resilience at the IC terminals 15, atleast part of the test contact 20 at the first electrical contactingportion 24 may be formed of beryllium copper material. In addition, itcan be seen in FIG. 5A that the first electrical contacting portion 24comprises a radius 44 suitable for sliding against the IC terminal 15 sothat the test contact 20 can be rotated into the second position.

The test contact 20 shown in FIG. 5 comprises a body portion 40 ofgenerally constant thickness and the head portion 32 has a protrudingportion 42 of generally reduced thickness relative to the body portion40. That is, the protruding portion 42 is reduced in thicknesssymmetrically towards the radius 44, which is suitable for slidingagainst the IC terminal 15, to provide sufficient contact force with theIC terminal 15 and the test terminal 12 of the load-board whistmaintaining balance of the test contact 20 under use. The symmetry ofthe test contact 20 enables its centre of gravity to be balanced andthus increases the lifespan of the test assembly 14. Also, the reducedthickness enables the test contact 20 to be used with finer pitch. ICdevices whilst. maintaining sufficient thickness of the test contact 20to engage a stop SO of the housing 18. It will be appreciated by thosepersons skilled in the art that the contact socket 22 formed in thehousing 18 is configured to receive the reducing thickness test contact20, for example with suitable thickness socket walls, to enhancedurability of the electrical interconnect assembly 10.

The protruding portion 42 also includes a surface which constitutes thefirst electrical contacting portion 24. The test contact 20 shown inFIG. 5 is particularly suitable for use with pad/unleaded type ICdevices. Pad/unleaded type IC devices require a higher contact force atthe pad—test contact interface than leaded type IC devices and, as such,damage to the IC terminals 15 and/or the test terminals 12 is morelikely.

Alternatively, the test contact 20 may comprise a body portion 40 ofgenerally constant thickness and the protruding portion 42 havinggenerally an enlarged thickness relative to the body portion 40, whichis more suited to leaded type IC devices. In a further alternative, justthe radius 44 of the protruding portion 42 has a greater thicknessrelative to the body portion 40 to form a headed pin, as shown in FIG.5. In this case, the enlarged radius 44 of the protruding portion 42 isalso symmetrical to ensure balance of the test contact 20 under use. Thereduced thickness of the body portion 40 relative to the headed pin alsoallows for finer pitched IC devices to be tested. Also, it will beunderstood that by maintaining a relatively large width at the secondelectrical contacting portion 26, the contact pressure at the testcontact—test terminal interface is maintained sufficiently low to avoiddamage to the test terminals 12.

It can also be seen in FIGS. 6 and 7 that the contact socket 22comprises a stop 50 to restrict rotation of the test contact 20. Thestop 50 acts on the test contact 20 to restrict vertical movement of thetest contact 20 relative to the vertical plane intersecting the testterminal 16, as well as frictionally restricting lateral movement,thereby further maintaining the co-planarity of the test contact 20.That is, during use of the test system 8, the IC device 16 is urged froma first position shown in FIG. 6 towards the interconnect assembly 10 toa second position shown in FIG. 7 which acts to rotate the test contact20 within the socket 22 to form an electrical connection between thetest terminals 12 and the IC terminals 15 of the IC device 16. This canbe seen more clearly in FIG. 8 where the IC device 16 is moved in thedirection of Arrow A.

FIG. 9 shows a test system 46 according to an embodiment of the presentinvention showing a plurality of the above described test contacts 20 intheir respective contact sockets 22. In this system 46, each testcontact 20 is configured in their respective contact socket 22 and eachcontact socket 22 is keyed to the corresponding foot portion 34 so thatthe amount of permitted rotation of each test contact 20 relative to therespective contact socket 22 is restricted. Furthermore, the arrangementof the contact socket 22 allows for air flow (shown by arrows 48 inFIG. 1) to cool the IC device 16 and the electrical interconnectassembly 10 during use.

Modifications and variations as would be apparent to a skilled addresseeare deemed to be within the scope of the present invention.

We claim:
 1. An electrical test contact for electrically connecting atest terminal of an IC test assembly with an IC terminal of an IC devicein an electrical interconnect assembly, comprising: a first electricalcontacting portion for electrically engaging said IC terminal of an ICdevice during use; a second electrical contacting portion fixed to saidfirst electrical contacting portion for electrically engaging said testterminal of a test assembly during use, said second electricalcontacting portion having a curved surface for rotably engaging saidtest terminal during use; a first resiliently biasing member adapted toengage with said first electrical contacting portion; and a secondresiliently biasing member adapted to engage with said second electricalcontacting portion and to decelerate a force exerted on the testterminal of the test assembly by the second electrical contactingportion during use.
 2. An electrical test contact for electricallyconnecting a test terminal of an IC test assembly with an IC terminal ofan IC device in an electrical interconnect assembly according to claim1, wherein said first resiliently biasing member has an elongatedcylindrical shape.
 3. An electrical test contact for electricallyconnecting a test terminal of an IC test assembly with an IC terminal ofan IC device in an electrical interconnect assembly according to claim1, wherein the arrangement of the first and second electrical contactingportions and the first and second resiliently biasing members is suchthat, during use, when the first electrical contacting portion is pusheddownwards, said second electrical contacting portion acts as a pivotalong its said curved surface.
 4. An electrical test contact forelectrically connecting a test terminal of an IC test assembly with anIC terminal of an IC device in an electrical interconnect assemblyaccording to claim 1, wherein said second resiliently biasing member isadapted to prevent said test contact from contacting said housing.
 5. Anelectrical test contact for electrically connecting a test terminal ofan IC test assembly with an IC terminal of an IC device in an electricalinterconnect assembly according to claim 1, wherein said secondresiliently biasing member has an elongated cylindrical shape.
 6. Anelectrical test contact for electrically connecting a test terminal ofan IC test assembly with an IC terminal of an IC device in an electricalinterconnect assembly according to claim 1, wherein said first andsecond electrical contacting portions are formed of electricallyconductive material.
 7. An electrical test contact for electricallyconnecting a test terminal of an IC test assembly with an IC terminal ofan IC device in an electrical interconnect assembly according to claim1, wherein said first and second electrical contacting portions areformed of metal.
 8. An electrical test contact for electricallyconnecting a test terminal of an IC test assembly with an IC terminal ofan IC device in an electrical interconnect assembly according to claim7, wherein said metal comprises NiPdAu plating.
 9. An electrical testcontact for electrically connecting a test terminal of an IC testassembly with an IC terminal of an IC device in an electricalinterconnect assembly according to claim 1, wherein said first andsecond resiliently biasing members are formed of an elastomericmaterial.
 10. An electrical test contact for electrically connecting atest terminal of an IC test assembly with an IC terminal of an IC devicein an electrical interconnect assembly according to claim 1, whereinthere is a sliding action between said second electrical contactingportion and said test terminal during use.